<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    var i = 1
    var str = 'zsss'
    var f=0.1
    console.log(typeof f);
    i = new Number()
    console.log(typeof i)
    console.log(i instanceof Number)

    function f1() {
        alert(4)
    }

    function f2() {
        var str = "aza";
        var str;
        // var str = "zaz"
        console.log(str)

        var strs = [1,2,3,"aaa",44]
        console.log(strs)

        var user={
            userName:"zs",
            age:18
        }
        console.log(user.age)
        console.log(user['userName'])

        user.aaa = 'aaa'
        user['aaa']=111
        console.log(user)

        if(NaN){
            console.log(true)
        }else{
            console.log(false)
        }

        var list = ["a","b","c","d"]
        list.contribute = 'aaa'
        console.log(list)
        for (var j = 0; j <list.length; j++) {
            console.log(list[j])
        }
        for(item in list){
            console.log(item)
            console.log(list.item)
        }
    }
</script>

<button onclick="f2()">点击就送</button>

</body>
</html>